Refrigerating system



Jan..26, 1937. w. w. HIGHAM 2,068,677

REFRIGERATING SYSTEM Fi led Feb. 24, 1.936

ATTORNEY.

Patented Jinn. 26, 1937 ATET OFFICE Claims. (Cl. 62-115) This invention relates to a refrigerating systemv which embodies a compressor, a condenser, a reservoir for liquefied refrigerant, and an evaporator where the liquid refrigerant is vaporized 5 for refrigerating purposes and through which system the refrigerant is circulated.

Among the objects of the invention is the provision of a refrigerating system or mechanism which operates with increased efficiency even though such units as the compressor, condenser and evaporator are substantially the same in structure and capacity as a similar mechanism which does not embody the invention; also to provide a refrigerating mechanism which assures that the expanded refrigerant entering the compressor is of gaseous form, thus eliminating a condition where some liquid refrigerant may pass into the compressor with resultant undesirable operation. To these ends the system embodies a structure for effecting a heat transfer between the suction line carrying expanded refrigerant from the evaporator to the compressor and the liquefied refrigerant about to be passed to the evaporator. A further object of the invention is to provide a structure wherein a maximum heat transfer is obtained with a minimum exposed surface. More'specifically, the heat transfer is preferably efiected by arranging the suction line for the expanded gases in heat transfer n relation with the reservoir or receiver of liquefied refrigerant. These and other objects will become more apparent as a detailed description is considered in conjunction with the accompanying drawing.

Fig. 1 is a general view showing somewhat diagrammatically a refrigerating mechanism constructed in accordance with the invention, with the mechanism mounted in a cabinet which is shown largely in section.

40 Fig. 2 is a detailed view with parts cut away showing the receiver tank and heat exchange arrangement.

At the outset it may be stated that while the drawing shows a refrigerator which may be classified as the general household type, it is to be appreciated that the invention is not limited to such use, and is in fact particularly applicable to self-contained units such as ice cream freezers, preserve cabinets, air conditioning units,

and. in fact all systems where the line, herein called the suction line, for carrying expanded gases from the evaporator to the condenser is relatively short. However, the invention is not limited to a situation where the suction line is short, or in other words where the evaporator is in close proximity to the condenser and other mechanism.

In the drawing a conventional type of cabinet is shown at I with a compartment 2 to be refrigerated. In this compartment a suitable 5 evaporator or expansion coil is disposed, as shown at 3, the structure of which is subject to many variations. Leading into this coil is a liquid refrigerant line 4 which discharges liquid into the evaporator through a controlling expansion valve 10 5. This expansion valve may be a thermostatically controlled type of valve, to which end it may have a tube or feeler leg 6 containing a heat responsive fluid and held in heat exchange relation with the suction line 1 by means of suit- 15 able clamping and housing elements 8. The structure of such an expansion valve and the thermostatic control thereof are well known to those versed in the art, and so far as the present invention is concerned the structure need not be detailed herein. The suction line I is designed to carry the gasified refrigerant away from the evaporator. Where the suction line is of considerable length it preferably is insulated to preserve the coldness of the gasified refrigerant for the purpose which will later appear. Such insulation is shown at 9.

There is a suitable compressor as shown at I 0 into which the suction line 1 connects as illustrated, and this may be operated by a suitable motor ll through the means of a belt I2. The compressed refrigerant passes out of the compressor into a pipe line l3 which extends to a suitable condenser I l, and a fan 15 on the motor shaft sets up a current of air through the condenser. The compressed gases are condensed into liquid form in the condenser, and a receiver tank or reservoir is shown at l6 connected to the condenser for the purpose of receiving and storing the liquefied refrigerant. The refrigerant 40 line 4 connects into the reservoir l6 and a suitable service valve l'l may be used at this point.

For convenience the reference character 1 has been used to illustrate the suction line running out of the evaporator and also running into the 45 compressor, although this line may be constituted by separate tubes. The line i is disposed in heat transfer relation with the stored liquid refrigerant in the tank 65. To this end one or more runs or loops of tube la. may be disposed 5 within the tank with the ends thereof available for connection through a wall of the tanlr and with the portions of the line l connected therewith as at 2B. The connections 28 may be separable and may take the form of service valves. 5

In demonstrating the operation and emciency of this structure it is thought that it is best to recite comparative figures ascertained by calculation based upon standard ton conditions, i. e. the refrigerating effect required to melt one ton of ice in 24 hours. These figures are also based on the use of dichlorodifiuoromethane (CCLzFz) as a refrigerant. The figures would vary with a different refrigerant. These comparisons relate to machines which are identical save for the fact that one was equipped with the heat exchanger and one was not so equipped. The figures thus ascertained by this calculation are in a sense theoretical, but nevertheless show the difference in operating conditions. In a-refrigerating mechanism, without the heat transfer, the line 1 extends directly from the evaporator to the compressor. In both cases the temperature of the evaporator-5 F. the pressure within the evaporator in pounds per square inch, in both cases,26.5. In the structure without the heat exchanger the temperature in the suction line,-.- 5 F., and the gases to be compressed entered the compressor at this temperature and this is, of course, assuming a more or less theoretical condition where there is absolutely no heat transfer from the suction line to the ambient atmosphere or structure between the evaporator and the compressor. With the heat transfer device the expanded gases enter the suction line ll at 5 F., but raise to 45 F. by the heat transfer device and enter the compressor at this temperature. This again visualizes a theoretical situation where there is no loss to the ambient atmosphere. Pressure in the condenser in both instances- 107.9 pounds per square inchand the atmospheric temperature at the condenser was calculated as being the same in both instances. The temperature of the refrigerant after compression,100 F. without the heat transfer device, and 140 F. with the heat transfer device. The temperature of the liquid refrigerant in the line 4 and at the time of entering the evaporator,- 86 F. without the heat exchanger, and 60 F. without the heatexchanger,and 60 F. with the heat exchanger.

Therefore, it will at once be observed that: The cold gases leading from the evaporator are heated up before reaching the compressor. This assures that all of the refrigerant is gasified and that no liquid refrigerant reaches the compressor which would otherwise interfere with compressor operation and create a boiling action which tends to draw the oil in the compressor into the refrigerant line. The temperature of the liquid refrigerant at the time it enters the evaporator is reduced with the result that the sensible heat of the liquid which has to be dissipated by the evaporator is lowered so that more work is done by the evaporator in actually refrigerating the compartment and less in dissipating the sensible heat of the refrigerant, thus increasing the efiiiciency.

It will be noted that since the compressed refrigerant enters the condenser at a higher temperature that more work is done by the condenser and more heat rejected thereby. But the condenser is amply capable of doing this extra work. For example, based on the standard ton conditions, the condenser would eject-61.79 B. t. u. per pound of refrigerant without the heat exchanger, and 74.44 B. t. u. per pound with the heat exchanger. In fact, more work is placed upon the compressor, in this, that comparative calculations in one case show that without the heat exchanger the work of the compressor when translated into B. t. u.-10.'72 B. t. u. per pound of refrigerant without the heat exchanger, and

12.27 B. t. u. per pound refrigerant with the heat exchanger. The refrigerating effect at the evaporator,-5l.07 B. t. u. per pound of refrigerant without the heat exchanger, and 62.17 B. t. u. per pound with the heat exchanger. Moreover, less refrigerant is circulated with the present invention; without the heat exchanger 3.92 pounds of refrigerant circulated per minute,

- per ton, per day, and with the heat exchanger 3.22 pounds of refrigerant per minute, per ton, p r day.

Briefly reiterating, the liquid refrigerant is cooled before it enters the evaporator, so that less sensible heat of the refrigerant has to be dissipated and more refrigeration accomplished. The expanded refrigerant is warmed by the heat exchanger and thus a condition is assured wherein the refrigerant is completely gasified before reaching the compressor. These conditions place more work on the compressor and on the condenser, but these units are outside of the refrigerating compartment, and it is feasible to do this work and dissipate or reject the heat at the condenser, thus increasing the refrigerating efiiciency at the evaporator. With two machines identical in structure, one Without the heat exchanger and one with the heat exchanger, the

level of the liquefied refrigerant in the condenser would in all probability be lower where a heat exchanger is used than where a heat exchanger is not used, since more work and time is required for the condenser to cause the refrigerant to liquefy. Moreover, the heat transfer is effected in a simple expedient manner by merely arranging the suction line in heat transfer relation with the liquid refrigerant in the receiver tank. The comparative figures given above, to show the operation and efiiciency of the system, are calculated and based on standard ton conditions, but obviously the intention is in no way limited to such figures and temperatures, as they are given merely as an example.

In some commercial structures, as for example, ice cream storage cabinets or the like, the receiver tank, as well also as the compressor and condenser, may be in close proximity to the evaporator, in which event it may not be necessary to insulate the suction line from the ambient atmosphere. However, where the receiver tank is more or less remote from the evaporator the suction line should be insulated to obtain the most efficient results of the invention. The point is to cool the liquid refrigerant by the expanded gases, as well also as to heat the expanded gases by the refrigerant. Therefore, the most efficient condition is where the expanded gases are disposed in heat transfer relation with the liquid in the tank at the lowest feasible temperature. If the suction line I has considerable length the gases would be warmed by the ambient atmosphere in their travel through the suction line, with the result that by the time the gases were disposed in heat transfer relation with the liquid refrigerant, the temperature of the gases would be raised, and the liquid refrigerant would not be cooled to such a low degree. In the drawing attached hereto the suction line may be several feet long, and it is shown as being insulated. Of course, this is only an example; sometimes the suction lines are much longer, as for example,

where the receiver tank, together with the compressor and condenser, are located in a difierent room, or perhaps in the basement. Also where the receiver tank is thus remotely situated and the temperature of the liquid refrigerant is lowered to say 60, the refrigerant may become warmed by the ambient atmosphere as it flows through the line 4 to the evaporator. Thus in some instances it may be desirable to insulate a refrigerant line.

I claim:

1. A refrigerating apparatus comprising in combination, a compressor, a condenser, a receiver tank for storing liquid refrigerant, an evaporator, a tube line extending from the receiver tank to the evaporator, a suction tube line extending from the evaporator to the compressor, and one or more runs of tubing constituting part of the suction tube line and disposed directly within the receiver tank, whereby heat is transferred to the expanded refrigerant in the suction line to assure complete vaporization thereof, and the sensible heat of the liquid refrigerant in the tank and which is about to be conveyed to the evaporator is reduced.

2. A refrigerating apparatus of the direct expansion type comprising, a compressor, a condenser, a receiver tank for receiving from the condenser and for storing liquid refrigerant, an evaporator, a tube line running from the receiver tank to the evaporator for conveying liquid refrigerant to the evaporator, a controlling expansion valve located adjacent the evaporator and into which the tube line connects for controlling the flow of liquid refrigerant into the evaporator, a suction tube line extending from the evaporator to the compressor, and one or more runs of tube constituting a part of the suction line and disposed completely within the receiver tank and in direct heat exchange relation with the liquid refrigerant therein, whereby the expanded refrigerant is heated by the liquid refrigerant and complete vaporization thereof is insured before the same enters the compressor, and whereby the sensible heat of the liquid refrigerant is reduced before the same passes through the expansion valve.

evaporator, a suction tube line extending from the evaporator to the compressor, said suction tube line having a portion which is in direct heat exchange relation with the liquid refrigerant in the receiver tank, whereby the expanded refrigerant is heated and complete vaporization is insured before the same enters the compressor, and whereby the sensible heat of the liquid refrigerant is reduced before the same enters the expansion valve.

4. A refrigerating apparatus comprising in combination, an evaporator, a compressor, a suction line for expanded refrigerant extending from the evaporator to the compressor, a receiver tank for liquid refrigerant, a tube line extending from the tank to the evaporator for carrying liquid refrigerant to the evaporator, said suction line having a part Within the receiver tank and in direct exchange relation with the liquid refrigerant in the tank, whereby the expanded cooled refrigerant in the suction line lowers the sensibleheat of the liquid refrigerant to thus reduce the sensible heat to be dissipated at the evaporator, thus increasing the efiiciency of the refrigerating effect of the evaporator and thereby increasing the temperature of the expanded refrigerant in the suction line to insure vaporization thereof before the same enters the compressor, and a condenser between the compressor and receiver tankfor receiving the compressed refrigerant and which has sufficient capacity to dissipate the heat of the compressed refrigerant plus the additional heat acquired from the liquid refrigerant to liquefy the compressed refrigerant.

5. A refrigerating apparatus comprising in combination, a compressor, a condenser, a receiver tank for storing liquid refrigerant, an evaporator, a tube line extending from the receiver tank to the evaporator, a suction tube line extending from the evaporator to the receiver tank, insulation around said suction tube line for preserving the coldness of the expanded gases from dissipation by the ambient atmosphere, one or more runs of tubing connected to the suction tube line and disposed directly within the receiver tank whereby heat is transferred to the expanded refrigerant to assure complete vaporization thereof, and the sensible heat of the liquid refrigerant in the tank which is about to be conveyed to the evaporator is reduced, and another suction tube line connecting to said one or more runs of tubing in the receiver tank and extending to the compressor, said condenser having a capacity sufficient to condense the refrigerant and to dissipate the additional heat acquired by the returning gases from the liquid refrigerant in the receiver tank.

WM. W. HIGHAM. 

